This proposal describes a large-scale, longitudinal follow-up of a sample of children selected at age two years whose behavior was characterized by parents as problematic (aggressive and destructive). These children were assessed in the laboratory and using parent questionnaires in order to characterize their emotional, social and family functioning. Important differences between problem children and control children emerged that suggest that, rather than being transient phenomena, early behavior problems might have important developmental implications. The proposed investigation will involve multiple assessments of these children and their families in multiple contexts at several important developmental periods from age four to age seven. In addition, a second cohort of two-year-olds will be added to the study. The assessments of both cohorts will focus on five specific and interrelated domains of functioning: child characteristics, parent functioning, family environment, school adjustment and peer relationships. The study will examine the transactional role of functioning in these domains in the multiple, longitudinal pathways that may be associated with early-onset behavior problems, as well as the factors that may be associated with resilience despite the risk associated with such early problems. The proposed project is both significant and timely because, despite the clear importance of early identification of children with acting-out, aggressive behavior problems, few longitudinal studies have been conducted with children younger than 3 or 4 years of age examining the early display of these types of behaviors, the multiple factors contributing to such behavior, and the complex pathways to later psychosocial functioning.